I've got a couple of questions.
one, did they tell the appropriate ministers or parliamentarians that they opposed, supported or were not taking a position on your requested changes?
two, was the letter they sent to you a statement that they were opposing those changes or taking a public position in opposition to them, or did they simply not want to get involved in whatever you were up to?
Because there's a world of difference between a union or public body taking a position opposing something, versus simply not wanting to get involved in whatever the person who has written to them is doing. I'm not against the changes you are hoping for here, but the context of the letter and their actions relating to it makes a big difference here. Also as Cap Bloggs has said, on what date approximately was the letter sent?